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Genome-wide analysis of transcription factor E2F1 mutant proteins reveals that N- and C-terminal protein interaction domains do not participate in targeting E2F1 to the human genome.

ABSTRACT: Previous studies of E2F family members have suggested that protein-protein interactions may be the mechanism by which E2Fs are recruited to specific genomic regions. We have addressed this hypothesis on a genome-wide scale using ChIP-seq analysis of MCF7 cell lines that express tagged wildtype and mutant E2F1 proteins. First, we performed ChIP-seq for tagged wt E2F1. Then, we analyzed E2F1 proteins that lacked the N terminal SP1 and cyclin A binding domains, the C terminal transactivation and pocket protein binding domains, and the internal marked box domain. Surprisingly, we found that the ChIP-seq patterns of the mutant proteins were identical to that of wt E2F1. However, mutation of the DNA binding domain abrogated all E2F1 binding to the genome. These results suggested that the interaction between the E2F1 DNA binding domain and a consensus motif may be the primary determinant of E2F1 recruitment. To address this possibility, we analyzed the in vivo binding sites for the in vitro-derived consensus E2F1 motif (TTTSSCGC) and also performed de novo motif analysis. We found that only 12% of the ChIP-seq peaks contained the TTTSSCGC motif. De novo motif analysis indicated that most of the in vivo sites lacked the 5â half of the in vitro derived consensus, having instead the in vivo consensus of CGCGC. In summary, our findings do not provide support for the model that protein-protein interactions are involved in recruiting E2F1 to the genome, but rather suggest that recognition of a motif found at most human promoters is the critical determinant. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf

ORGANISM(S): Homo sapiens

PROVIDER: GSE28286 | GEO | 2011/04/04

REPOSITORIES: GEO

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Project description:Previous studies of E2F family members have suggested that protein-protein interactions may be the mechanism by which E2Fs are recruited to specific genomic regions. We have addressed this hypothesis on a genome-wide scale using ChIP-seq analysis of MCF7 cell lines that express tagged wildtype and mutant E2F1 proteins. First, we performed ChIP-seq for tagged wt E2F1. Then, we analyzed E2F1 proteins that lacked the N terminal SP1 and cyclin A binding domains, the C terminal transactivation and pocket protein binding domains, and the internal marked box domain. Surprisingly, we found that the ChIP-seq patterns of the mutant proteins were identical to that of wt E2F1. However, mutation of the DNA binding domain abrogated all E2F1 binding to the genome. These results suggested that the interaction between the E2F1 DNA binding domain and a consensus motif may be the primary determinant of E2F1 recruitment. To address this possibility, we analyzed the in vivo binding sites for the in vitro-derived consensus E2F1 motif (TTTSSCGC) and also performed de novo motif analysis. We found that only 12% of the ChIP-seq peaks contained the TTTSSCGC motif. De novo motif analysis indicated that most of the in vivo sites lacked the 5M-CM-"M-BM-^@M-BM-^Y half of the in vitro derived consensus, having instead the in vivo consensus of CGCGC. In summary, our findings do not provide support for the model that protein-protein interactions are involved in recruiting E2F1 to the genome, but rather suggest that recognition of a motif found at most human promoters is the critical determinant. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf 9 total ChIP-seq datasets; four different HA-ER-E2F1 mutants, and one HA ER E2F1 wild type dataset done in duplicate, from 5 different stable cell lines derived from MCF7 cells; Three Input replicates from 2 different stable cell lines derived from MCF7 cells; HA ER E2F1 wild type duplicate dataset from MCF7 stable cells; 1 HA ER E2F1 DBDmut replicate from MCF7 stable cells cells, 1 HA ER E2F1M-CM-^NM-BM-^TC replicate from MCF7 stable cells cells, 1 HA ER E2F1M-CM-^NM-BM-^TN/C replicate from MCF7 stable cells cells, 1 HA ER E2F1M-CM-^NM-BM-^TMB replicate from MCF7 stable cells cells, 1 HA ER E2F1M-CM-^NM-BM-^TMB replicate from MCF7 stable cells cells, 3 Input replicates from MCF7 stable cells cells.

Project description:Recent genome-scale ChIP-chip studies of transcription factors have shown that a low percentage of experimentally determined binding sites contain the consensus motif for the immunoprecipitated factor. In most cases, differences between in vivo target sites that contain or lack a consensus motif have not been explored. We have previously shown that most sites to which E2F family members are bound in vivo do not contain E2F consensus motifs. The main purpose of this study was to develop an understanding of how E2F binding specificity is achieved in vivo. In particular, we have addressed how E2F family members are recruited to core promoter regions that lack a consensus motif and are excluded from other regions that contain a consensus motif. Using promoter and ENCODE arrays, we have shown that the predominant factors specifying whether E2F is recruited to an in vivo binding site are a) the site must be in a core promoter and b) the promoter region must be utilized as a promoter by the transcriptional machinery in that particular cell type. We have tested three models for recruitment of E2F to core promoters lacking a consensus site, including a) indirect recruitment, b) looping to the core promoter mediated by an E2F bound to a distal consensus motif, and c) assisted binding of E2F to a site that weakly resembles an E2F consensus motif within the core promoter. To test these models, we developed a new in vivo assay, termed eChIP, which allows analysis of transcription factor binding to isolated promoter fragments. Our findings suggest that in vivo a) the presence of a consensus motif is not sufficient to recruit E2Fs, b) E2Fs can bind to isolated regions that lack a consensus motif, and c) binding can require regions other than the best match to the E2F PWM in the core promoter. Keywords: E2F, ChIP-chip, transcription factor binding, consensus motifs 37 ChIP-chip arrays (of these, 14 array sets are biological duplicates). 22 samples are included in this series, the rest can be found in supplementary info to the following papers: Xu 2007, Jin 2006, Komashko 2008

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Genome-wide analysis of transcription factor E2F1 mutant proteins reveals that N- and C-terminal protein interaction domains do not participate in targeting E2F1 to the human genome.

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